This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. AIM-HIGH is a multicenter, prospective, randomized, double-blind, parallel-group, active comparator trial of simvastatin (statin monotherapy) versus extended-release niacin plus simvastatin (combination therapy) in high-risk patients with established vascular disease (i.e., those who have a 10-year risk of an event of >=20%) and atherogenic dyslipidemia (low HDL-C and high triglycerides). The hypothesis of AIM-HIGH is that combination anti-dyslipidemic therapy will be superior to statin monotherapy alone when used as secondary prevention in reducing long-term clinical events in patients with documented vascular disease and atherogenic dyslipidemia. Potentially eligible participants must meet one or more of the following criteria for established vascular disease. Documented coronary artery disease (CAD), documented cerebrovascular disease, or documented symptomatic PAD. During a 3-5 year follow-up, the study will compare efficacy and safety of statin monotherapy versus combination therapy at comparable levels of on-treatment LDL-C, to reduce the risk for clinical events or hospitalization for high-risk NSTE acute coronary syndrome) in vascular disease patients with atherogenic dyslipidemia (low HDL-C and high triglycerides).